FEC (Forward Error Correction) is an error control manner. When data on which FEC coding is performed is decoded at a receive end, a bit error that occurs in a transmission process of the data may be found and corrected. Therefore, an FEC technology improves transmission reliability and has wide application in long-distance transmission. In addition, to further correct a bit error, an interleaving technology may further be used. The interleaving technology can disperse, to an utmost extent, centralized burst bit errors over a channel transmission process, so as to improve a bit error correction capability of the receive end. FIG. 1 is a schematic diagram of processing performed by a transmit end on a data stream according to the prior art. In FIG. 1, FEC coding is first performed on the data stream at the transmit end, then channel interleaving is performed on the data stream, and then the data stream is sent. FIG. 2 is a schematic diagram of processing performed by a receive end on a data stream according to the prior art. In FIG. 2, at the receive end, processing such as de-interleaving and FEC decoding is performed on the data stream on which channel balancing is performed, and finally decision is performed on the decoded data stream to obtain a data stream sent by a transmit end.
As a transmission rate in a transmission system increases, for example, a transmission rate that is initially 40 Gb/s is now 100 Gb/s and may even be up to 400 Gb/s in the future, a bit error amount of burst bit errors that occur when a data stream is being transmitted over a channel is increasingly large. If the method for processing a received data stream by a receive end in FIG. 2 is still used, only a small part of the burst bit errors can be corrected, and consequently a capability of the receive end on correctly correcting a bit error is degraded, and a system gain is reduced.